Line driver amplifiers remain a bottleneck in modern analog circuit design. Their integration with other analog circuit components is problematic. One reason for this is that the need to employ relatively large magnitude supply voltages prevents realizing the advantages that would result from using finer and much faster integrated circuit technology. Other reasons include large power consumption, and sensitivity to noise coming from power supplies and the integrated circuit substrate. A line driver amplifier should have well-controlled quiescent currents flowing in its output transistors and have the ability to supply significantly larger currents during its transient state. The ability to supply large currents should not be compromised by non-linear open-loop gain characteristics of the line driver amplifier, because any non-linearity in the line driver characteristic translates into distortion, even though the distortion is somewhat reduced when feedback is employed.
Indeed, in known line driver amplifiers there is a significantly sharp transient in the open-loop gain input-output voltage transfer function that is extremely undesirable. Indeed, abrupt transitions in the open-loop gain transfer function result in non-linearity and must be avoided.